The iambic trimeter derives its name from its essential shape, which is three metrical units (hence trimeter) which are each basically iambic in form. The iambic metron has the following shape (where the x is an anceps, the - is a longum, and the u is a brevis):
Hence, reversing the current running though a wire will have the affect of reversing the direction of the magnetic force at a point some distance away from the wire. The affect that this has on the overall magnetic field depends on the shape of the wire.
But when the charge is in motion (current), a magnetic field is produced perpendicular to its direction of propagation. Say, If you pass current through a straight wire, magnetic field is formed around the wire in the form of circular rings (could affect compass or metal fillings nearby).